“Annoying: The Science of What Bugs Us” explains why some things – like overhearing a cell phone conversation, as opposed to a two-way conversation – are particularly grating.

“Annoyance is probably the most widely experienced and least studied of all human emotions…” write the authors, Joe Palca and Flora Lichtman, whose book is excerpted at NPR. Palca and Lichtman cover science for the public radio station.

They say much research literature is devoted to anger and aversion, but little on explaining annoyances.

So why is overhearing a cell phone conversation – at the gym, on the bus – so irritating? Turns out it’s not just the intrusiveness of the noise, but the fact that you’re listening to half a conversation, dubbed a “halfalogue.”

“Your brain goes into this mode where you start trying to predict what that person is going to say next,” Lichtman, of NPR’s “Science Friday,” told Morning Edition.

“The thing that’s frustrating about a cellphone conversation is that it’s very hard to predict, which is one of the things that we found makes something annoying.”